1. Field of the Invention
This invention relates to a machine for shearing films of thermoplastic material, such as PVC, polyethylene, polypropylene, etc.
2. Description of the Prior Art
It is known that thermoplastic materials like PVC, polyethylene, polypropylene, etc. for various uses, such as shopping bags, packing sacks, greenhouse awnings, etc., are recovered after use to be recycled to prepare new products. To this end the recovered waste is run through a series of regeneration operations, the first of which is shearing.
Shearing of the recovered waste is currently effected in so-called mills, that is in cylinders generally cylindrical in shape arranged with the cylinder axis vertical to the ground, with internal blades which shear the material while rotating about a shaft coincident with the geometric axis of the cylindrical container. This shearing system has numerous disadvantages. First of all, the blades are subjected to considerable wear and tear during use, and it is time-consuming to replace them and sharpen them and their expensive attachments. If the material to be sheared in the mill is damp, it "packs", that is it sticks to the walls of the drum of the container during operation. Moreover, the presence of foreign bodies in the recovered material inside the mill cannot be opportunely detected, that is, rotation of the blades cannot be stopped before they are damaged. Finally, and most seriously, electrical energy consumption is considerable, also in relation to the power used and the recurrence of its costs in billing.
Currently, if the above described mills are not used, the recovered material must be washed in its original bulky dimensions, that is in pieces of considerable size. However, this leads to high electricity costs in all the operations subsequent to shearing.